1. Field of the Invention
The present invention relates to an interpolation apparatus for improving the resolution; more particularly, the present invention relates to an interpolation apparatus for improving the resolution of an optical encoder.
2. Description of the Prior Art
The optical encoder of the prior art generates a sine output wave with an optimal phase difference of 90 degrees and duty cycles consisting 50% positive and negative cycles, when it couples with a code strip or code wheel corresponding to the resolution.
Please refer to FIG. 1. FIG. 1 is a schematic diagram illustrating the sine output wave 8 generated based on the corresponding code strip 6 of the prior art. The code strip 6 of the prior art has a plurality of blocks with black and white color alternating with each other. The oblique line area on the code strip 6 in FIG. 1 represents the black block 7. The alternated black and white color pattern on the code strip 6 is detected by the light detection element, and the corresponding sine wave is outputted by the optical encoder. When the detection element detects the black block 7, the optical encoder outputs a low level value wave. On the contrary, if the detection element detects the white block, the optical encoder outputs a high level value wave. The output wave of this kind of optical encoder can be used for controlling the movement and speed of the motor.
As disclosed in U.S. Pat. No. 6,355,927, a signal generator generates signals of A, nA, B, nB, fractional A, and fractional B to improve the resolution of an optical encoder. However, this method must be used with complicated circuit to operate and to generate the six different signals mentioned above. Hence, this method is very complicated.
A general motor revolves by using signals to control the revolving movement and directions, and a signal must be an analog signal or a digital signal. By controlling the resolution of the analog signal and the digital signal, the revolving movement and directions of the motor can be precisely controlled. Because the digital signal is not continuous, it has a lower resolution. Hence, the digital signal is used to control the motor to revolve in larger scale. Because the analog signal is continuous, it has a higher resolution. Hence, the analog signal is used to control the motor to revolve in smaller scale. Therefore, the motor can be precisely controlled by the cooperation of the digital signal and the analog signal.
The main objective of the present invention is to improve the resolution of the digital signal to precisely control the motor.